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[xz/debian.git] / src / liblzma / lzma / lzma2_encoder.c

// SPDX-License-Identifier: 0BSD

///////////////////////////////////////////////////////////////////////////////
//
/// \file       lzma2_encoder.c
/// \brief      LZMA2 encoder
///
//  Authors:    Igor Pavlov
//              Lasse Collin
//
///////////////////////////////////////////////////////////////////////////////

#include "lz_encoder.h"
#include "lzma_encoder.h"
#include "fastpos.h"
#include "lzma2_encoder.h"


typedef struct {
        enum {
                SEQ_INIT,
                SEQ_LZMA_ENCODE,
                SEQ_LZMA_COPY,
                SEQ_UNCOMPRESSED_HEADER,
                SEQ_UNCOMPRESSED_COPY,
        } sequence;

        /// LZMA encoder
        void *lzma;

        /// LZMA options currently in use.
        lzma_options_lzma opt_cur;

        bool need_properties;
        bool need_state_reset;
        bool need_dictionary_reset;

        /// Uncompressed size of a chunk
        size_t uncompressed_size;

        /// Compressed size of a chunk (excluding headers); this is also used
        /// to indicate the end of buf[] in SEQ_LZMA_COPY.
        size_t compressed_size;

        /// Read position in buf[]
        size_t buf_pos;

        /// Buffer to hold the chunk header and LZMA compressed data
        uint8_t buf[LZMA2_HEADER_MAX + LZMA2_CHUNK_MAX];
} lzma_lzma2_coder;


static void
lzma2_header_lzma(lzma_lzma2_coder *coder)
{
        assert(coder->uncompressed_size > 0);
        assert(coder->uncompressed_size <= LZMA2_UNCOMPRESSED_MAX);
        assert(coder->compressed_size > 0);
        assert(coder->compressed_size <= LZMA2_CHUNK_MAX);

        size_t pos;

        if (coder->need_properties) {
                pos = 0;

                if (coder->need_dictionary_reset)
                        coder->buf[pos] = 0x80 + (3 << 5);
                else
                        coder->buf[pos] = 0x80 + (2 << 5);
        } else {
                pos = 1;

                if (coder->need_state_reset)
                        coder->buf[pos] = 0x80 + (1 << 5);
                else
                        coder->buf[pos] = 0x80;
        }

        // Set the start position for copying.
        coder->buf_pos = pos;

        // Uncompressed size
        size_t size = coder->uncompressed_size - 1;
        coder->buf[pos++] += size >> 16;
        coder->buf[pos++] = (size >> 8) & 0xFF;
        coder->buf[pos++] = size & 0xFF;

        // Compressed size
        size = coder->compressed_size - 1;
        coder->buf[pos++] = size >> 8;
        coder->buf[pos++] = size & 0xFF;

        // Properties, if needed
        if (coder->need_properties)
                lzma_lzma_lclppb_encode(&coder->opt_cur, coder->buf + pos);

        coder->need_properties = false;
        coder->need_state_reset = false;
        coder->need_dictionary_reset = false;

        // The copying code uses coder->compressed_size to indicate the end
        // of coder->buf[], so we need add the maximum size of the header here.
        coder->compressed_size += LZMA2_HEADER_MAX;

        return;
}


static void
lzma2_header_uncompressed(lzma_lzma2_coder *coder)
{
        assert(coder->uncompressed_size > 0);
        assert(coder->uncompressed_size <= LZMA2_CHUNK_MAX);

        // If this is the first chunk, we need to include dictionary
        // reset indicator.
        if (coder->need_dictionary_reset)
                coder->buf[0] = 1;
        else
                coder->buf[0] = 2;

        coder->need_dictionary_reset = false;

        // "Compressed" size
        coder->buf[1] = (coder->uncompressed_size - 1) >> 8;
        coder->buf[2] = (coder->uncompressed_size - 1) & 0xFF;

        // Set the start position for copying.
        coder->buf_pos = 0;
        return;
}


static lzma_ret
lzma2_encode(void *coder_ptr, lzma_mf *restrict mf,
                uint8_t *restrict out, size_t *restrict out_pos,
                size_t out_size)
{
        lzma_lzma2_coder *restrict coder = coder_ptr;

        while (*out_pos < out_size)
        switch (coder->sequence) {
        case SEQ_INIT:
                // If there's no input left and we are flushing or finishing,
                // don't start a new chunk.
                if (mf_unencoded(mf) == 0) {
                        // Write end of payload marker if finishing.
                        if (mf->action == LZMA_FINISH)
                                out[(*out_pos)++] = 0;

                        return mf->action == LZMA_RUN
                                        ? LZMA_OK : LZMA_STREAM_END;
                }

                if (coder->need_state_reset)
                        return_if_error(lzma_lzma_encoder_reset(
                                        coder->lzma, &coder->opt_cur));

                coder->uncompressed_size = 0;
                coder->compressed_size = 0;
                coder->sequence = SEQ_LZMA_ENCODE;

        // Fall through

        case SEQ_LZMA_ENCODE: {
                // Calculate how much more uncompressed data this chunk
                // could accept.
                const uint32_t left = LZMA2_UNCOMPRESSED_MAX
                                - coder->uncompressed_size;
                uint32_t limit;

                if (left < mf->match_len_max) {
                        // Must flush immediately since the next LZMA symbol
                        // could make the uncompressed size of the chunk too
                        // big.
                        limit = 0;
                } else {
                        // Calculate maximum read_limit that is OK from point
                        // of view of LZMA2 chunk size.
                        limit = mf->read_pos - mf->read_ahead
                                        + left - mf->match_len_max;
                }

                // Save the start position so that we can update
                // coder->uncompressed_size.
                const uint32_t read_start = mf->read_pos - mf->read_ahead;

                // Call the LZMA encoder until the chunk is finished.
                const lzma_ret ret = lzma_lzma_encode(coder->lzma, mf,
                                coder->buf + LZMA2_HEADER_MAX,
                                &coder->compressed_size,
                                LZMA2_CHUNK_MAX, limit);

                coder->uncompressed_size += mf->read_pos - mf->read_ahead
                                - read_start;

                assert(coder->compressed_size <= LZMA2_CHUNK_MAX);
                assert(coder->uncompressed_size <= LZMA2_UNCOMPRESSED_MAX);

                if (ret != LZMA_STREAM_END)
                        return LZMA_OK;

                // See if the chunk compressed. If it didn't, we encode it
                // as uncompressed chunk. This saves a few bytes of space
                // and makes decoding faster.
                if (coder->compressed_size >= coder->uncompressed_size) {
                        coder->uncompressed_size += mf->read_ahead;
                        assert(coder->uncompressed_size
                                        <= LZMA2_UNCOMPRESSED_MAX);
                        mf->read_ahead = 0;
                        lzma2_header_uncompressed(coder);
                        coder->need_state_reset = true;
                        coder->sequence = SEQ_UNCOMPRESSED_HEADER;
                        break;
                }

                // The chunk did compress at least by one byte, so we store
                // the chunk as LZMA.
                lzma2_header_lzma(coder);

                coder->sequence = SEQ_LZMA_COPY;
        }

        // Fall through

        case SEQ_LZMA_COPY:
                // Copy the compressed chunk along its headers to the
                // output buffer.
                lzma_bufcpy(coder->buf, &coder->buf_pos,
                                coder->compressed_size,
                                out, out_pos, out_size);
                if (coder->buf_pos != coder->compressed_size)
                        return LZMA_OK;

                coder->sequence = SEQ_INIT;
                break;

        case SEQ_UNCOMPRESSED_HEADER:
                // Copy the three-byte header to indicate uncompressed chunk.
                lzma_bufcpy(coder->buf, &coder->buf_pos,
                                LZMA2_HEADER_UNCOMPRESSED,
                                out, out_pos, out_size);
                if (coder->buf_pos != LZMA2_HEADER_UNCOMPRESSED)
                        return LZMA_OK;

                coder->sequence = SEQ_UNCOMPRESSED_COPY;

        // Fall through

        case SEQ_UNCOMPRESSED_COPY:
                // Copy the uncompressed data as is from the dictionary
                // to the output buffer.
                mf_read(mf, out, out_pos, out_size, &coder->uncompressed_size);
                if (coder->uncompressed_size != 0)
                        return LZMA_OK;

                coder->sequence = SEQ_INIT;
                break;
        }

        return LZMA_OK;
}


static void
lzma2_encoder_end(void *coder_ptr, const lzma_allocator *allocator)
{
        lzma_lzma2_coder *coder = coder_ptr;
        lzma_free(coder->lzma, allocator);
        lzma_free(coder, allocator);
        return;
}


static lzma_ret
lzma2_encoder_options_update(void *coder_ptr, const lzma_filter *filter)
{
        lzma_lzma2_coder *coder = coder_ptr;

        // New options can be set only when there is no incomplete chunk.
        // This is the case at the beginning of the raw stream and right
        // after LZMA_SYNC_FLUSH.
        if (filter->options == NULL || coder->sequence != SEQ_INIT)
                return LZMA_PROG_ERROR;

        // Look if there are new options. At least for now,
        // only lc/lp/pb can be changed.
        const lzma_options_lzma *opt = filter->options;
        if (coder->opt_cur.lc != opt->lc || coder->opt_cur.lp != opt->lp
                        || coder->opt_cur.pb != opt->pb) {
                // Validate the options.
                if (opt->lc > LZMA_LCLP_MAX || opt->lp > LZMA_LCLP_MAX
                                || opt->lc + opt->lp > LZMA_LCLP_MAX
                                || opt->pb > LZMA_PB_MAX)
                        return LZMA_OPTIONS_ERROR;

                // The new options will be used when the encoder starts
                // a new LZMA2 chunk.
                coder->opt_cur.lc = opt->lc;
                coder->opt_cur.lp = opt->lp;
                coder->opt_cur.pb = opt->pb;
                coder->need_properties = true;
                coder->need_state_reset = true;
        }

        return LZMA_OK;
}


static lzma_ret
lzma2_encoder_init(lzma_lz_encoder *lz, const lzma_allocator *allocator,
                lzma_vli id lzma_attribute((__unused__)), const void *options,
                lzma_lz_options *lz_options)
{
        if (options == NULL)
                return LZMA_PROG_ERROR;

        lzma_lzma2_coder *coder = lz->coder;
        if (coder == NULL) {
                coder = lzma_alloc(sizeof(lzma_lzma2_coder), allocator);
                if (coder == NULL)
                        return LZMA_MEM_ERROR;

                lz->coder = coder;
                lz->code = &lzma2_encode;
                lz->end = &lzma2_encoder_end;
                lz->options_update = &lzma2_encoder_options_update;

                coder->lzma = NULL;
        }

        coder->opt_cur = *(const lzma_options_lzma *)(options);

        coder->sequence = SEQ_INIT;
        coder->need_properties = true;
        coder->need_state_reset = false;
        coder->need_dictionary_reset
                        = coder->opt_cur.preset_dict == NULL
                        || coder->opt_cur.preset_dict_size == 0;

        // Initialize LZMA encoder
        return_if_error(lzma_lzma_encoder_create(&coder->lzma, allocator,
                        LZMA_FILTER_LZMA2, &coder->opt_cur, lz_options));

        // Make sure that we will always have enough history available in
        // case we need to use uncompressed chunks. They are used when the
        // compressed size of a chunk is not smaller than the uncompressed
        // size, so we need to have at least LZMA2_COMPRESSED_MAX bytes
        // history available.
        if (lz_options->before_size + lz_options->dict_size < LZMA2_CHUNK_MAX)
                lz_options->before_size
                                = LZMA2_CHUNK_MAX - lz_options->dict_size;

        return LZMA_OK;
}


extern lzma_ret
lzma_lzma2_encoder_init(lzma_next_coder *next, const lzma_allocator *allocator,
                const lzma_filter_info *filters)
{
        return lzma_lz_encoder_init(
                        next, allocator, filters, &lzma2_encoder_init);
}


extern uint64_t
lzma_lzma2_encoder_memusage(const void *options)
{
        const uint64_t lzma_mem = lzma_lzma_encoder_memusage(options);
        if (lzma_mem == UINT64_MAX)
                return UINT64_MAX;

        return sizeof(lzma_lzma2_coder) + lzma_mem;
}


extern lzma_ret
lzma_lzma2_props_encode(const void *options, uint8_t *out)
{
        if (options == NULL)
                return LZMA_PROG_ERROR;

        const lzma_options_lzma *const opt = options;
        uint32_t d = my_max(opt->dict_size, LZMA_DICT_SIZE_MIN);

        // Round up to the next 2^n - 1 or 2^n + 2^(n - 1) - 1 depending
        // on which one is the next:
        --d;
        d |= d >> 2;
        d |= d >> 3;
        d |= d >> 4;
        d |= d >> 8;
        d |= d >> 16;

        // Get the highest two bits using the proper encoding:
        if (d == UINT32_MAX)
                out[0] = 40;
        else
                out[0] = get_dist_slot(d + 1) - 24;

        return LZMA_OK;
}


extern uint64_t
lzma_lzma2_block_size(const void *options)
{
        const lzma_options_lzma *const opt = options;

        if (!IS_ENC_DICT_SIZE_VALID(opt->dict_size))
                return UINT64_MAX;

        // Use at least 1 MiB to keep compression ratio better.
        return my_max((uint64_t)(opt->dict_size) * 3, UINT64_C(1) << 20);
}